Grinding noise from NP205
 

The truck is a 79 F350 4x4 and from what I can tell, the transfer case is making a grinding noise (quite loud) after hitting 30 plus mph and letting off the gas. The hubs are locked in and it has a new drive shaft. I don't hear any noise in 2W drive, only 4W drive. The noise is a heavy grinding noise and sounds like a person trying to shift manual for the first time. The only way to reduce the grinding is to give it some gas while slowing down.

The Hubs were pulled apart, cleaned and put back together not long ago. This was the first time out with it in the snow since I first got it just over a month ago. .
Thanks in advance.

Did it do it on the test drive (when you checked out the 4wd operation) before you bought it? Has a new (front?) d/s? Why? Are you doing 30 MPH in 4L or 4H?
Have you checked the fluid level/condition of the xfer case? Meaning strain some fluid thru a white clean cloth to see is there is metal shavings in the transfer case fluid?
Does it do it in both 4H and 4L? Were the hubs put back together correctly? Is the transfer case hot/to hot to touch after driving it?

I remove the front d/s (to include slip yoke) put it in 4H and drive it and see if you still hear the sound.

When I bought it I did go through the gears 4L, 4H, 2H and drove it in 2w for the most part. I only moved it for a few feet in 4 whee. Low and High to make sure they were working. There were no weird noises and all seemed normal.
The truck was jacked up 6 inches and after working on the truck I saw that the front drive shaft was the stock OEM shaft and you could grab it and move it back and forth sideways. I did my measurements the drive shaft place wanted and they made me one 2 inches longer.
I have not driven the truck yet in 4L only 4H and did not know I could not go 30mph in town with snow covered streets. This is bad?
The fluid in the transfer case is at the plug level, it is full. I was going to change out the fluid and change out all the seals in the transfer case within the next week or so, when I can get use of the shop again. "friend mechanic has a lift" Was the transfer case hot, I did not check, but can check that out today.
When I dump the transfer case fluid, I will be checking for metal filings.
I have not checked 4L since yesterday is basically the first time having it out. With the hubs locked and in 2 wheel drive, there is no problems. Only when it is in 4 wheel drive High and costing from 25 to 30mph. If I feather the gas peddle to match the speed of the driveshaft, "no load" the noise goes away.
The hubs were put back together the reverse of how they were, when I pulled them apart. I replaced the seals, cleaned and checked the bearings, repacked them and reassembled. Engaged the hubs after and checked to see if they were working and they were.

Interested to see what is figured out because I am having the same exact problem, even after rebuilding the transfer case. Hubs are new, wheel bearings good, u-joints.good. I am thinking either I have too much slop in a differential and the vibration is coming up the driveshaft, or maybe the shift forks in the transfer case should have been replaced when I rebuilt it.

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Well at least you checked the 4wd operation before you bought it. IMO I would of driven it a little further, beside the point now. So with the 6" lift kit and the side to side play in the d/s "Move it back and forth sideways" Where? (input/out put flange, slip yoke?) You decided to get a new d/s made and add 2" length. Did you take your measurements with the front suspension at full droop and compression? What does your front axle pinion angle look like?

30 MPH for 4L a little fast IMO. I like 4L for putting all the pulling power to the ground and not really going very fast. AGAIN IMO. But as far as 30 PLUS MPH in 4H mud, sand, soft soil, snow, ice, grass, gravel roads dirt track, and any other none hard packed/paved surface. Hammer down! So you never heard this sound before the hub re-grease? Did your truck have a single or double cardan u joint at the output flange on the fwd side of the xfer case? Before the new one was made?

Hubs locked in, 2wd on the xfer and no sound...interesting. Sounds like it might be in your front axle, and ring and pinion issue? Have you popped the cover and insp in there? I still would try to locate the sound by removing the front d/s and then try it and see it is the xfer case or the front axle.

The truck was not insured or plated to be on the road when I bought it and I was limited to speed when testing at the time of purchase. These trucks are very hard to find around here, especially in as good of shape as this one. So even though I knew at the time it needed a few things, This would not have scared me much, just the fact it could have helped in working out the price.
The drive shaft had side to side play at the slip yoke and was totally pooched. I was not the one to say, make it 2 inches longer, but the drive shaft manufacture. As for their instructions, they wanted the truck on the ground and measured centre to centre of each outer U joint. They also wanted to know the amount of difference with the wheels off the ground. The drive shaft was not lengthened but a totally new unit. As for single or double cardan, the truck had a single cardan and later after getting the new shaft made, I found out that most of these trucks came with a double, but it was too late and this one can't be modified to be double. If I want a double, another $1000 will do it on a new unit. So Im going to use the one I have unless there is a problem.
As for sound in 2wd and hubs locked, there is no grinding noise at all but there may be a slight whine from the dif or transfer case. The dana 60 front and back are 410's not sure if there would be any whine noise at all from them.
Your comment on the dif, I have not taken off the cover, but was one thing I was also going to do when doing the transfer case seal and gasket renewal. I did pop off the rear cover when working on the truck and it was indeed a farm truck and worked hard. What I thought was a bad U joint, "shifting from reverse to drive Ping" was not the U joint, but a lot of lash, possibly .030, and what is required is between .004 and .009. We replaced the shims that were warn and reset the lash and found it to be .008 when we were finished. So that said, it is possible that the front may be a problem even though by feel, could not detect excessive lash like the rear. So the grinding sound on deceleration, that sounded like jamming gears off and on, would be from the front dif?
In regards to your last question, removing the drive shaft and putting it in 4 wheel high, would reveal, that its the transfer case or the axel. So if there is grinding, it's the transfer case and no grinding, it's the axel?
Thanks for taking the time to help figure this out.

That is exactly it! Did you have that noise before all the work was done and did you figure it out since?

That is great news. So your video was in 4wd? So you went though 4L then down to N, 2H, 2L then back up to 2H. Did you try it in 4wd again to see if the noise was there? Mine only does it in 4wd.
One thing when re packing bearings, I was told to not use regular bearing grease in the hubs, but to use a lighter grease like white lithium. I didn't have any on hand so in went some regular grease. Not sure if it is too stiff for the inner workings to move well enough. To my comment on the grease, only little was used.

Cougar, with just a single joint at each end of the shaft, are your angles matched up? With lifts that high, it's common for them not to be within spec. I believe it's a pretty narrow range that you need to keep them in. Both in relation to each other, AND maximum angle compared to the shaft.
As was being discussed, it's one of the possibilities for your noise. Especially if that "grinding" could also be described as a "gear rattle" noise.

It's not uncommon for a vibration in the driveshaft to come and go under acceleration/deceleration transitions. It's also common for this vibration to be transmitted into the gearboxes and, whichever one has a loose mesh can rattle.
Heard it in many transmissions in fact. Not just transfer cases. But it still could be either one making the noise in sympathetic harmonics from the driveshaft u-joint angles.

If you don't have an angle finder, you can eyeball it if the angles are far enough off. Or take pictures from the side showing both joints/yokes and let us take a look too.
Can't hurt to at least rule it out.

Paul

Ok so side to side play in the slip yoke, pooched, got it. New d/s per shop instructions, (wheels off the ground='s unloaded suspension) got it. I believe the double cardan d/s helps with the d/s angle. I would remove the front d/s and take if for a drive. Put xfer case in 4H and see what it sounds like on a drive, and then 4L and listen again. Same grinding sound...sounds like a possible internal xfer case issue?

Hang in there with the sound hunt and locating the problem, and for sure keep us posted on what it is when you figure it out.

That's exactly what mine is doing. When in 4wd with hubs locked I hear it. Unlock the hubs it goes away no matter if it's in 4wd or 2wd. If I leave the hubs locked and switch to 2wd, no noise. I'm thinking differential noise traveling up driveshaft, but until I can get it up on blocks to run it while someone listens I can't be sure.

Ok, here are some pictures. The angle of the drive shaft is 18 degrees and that is if the truck is on level ground or no, it's a give or take. The upper U joint on the transfer case has been cleaned/opened up some to clear and there is at least .020 clearance. I will take it off shortly and go for a drive. Did you look at Paulstruck video he sent? it is the same noise and he managed to have the noise go away after unlocking the hubs and re-locking them as well as going thought the gears. What do you make of that? could the use of the wrong grease stop the full engagement of the hubs? You would thing it would be evident they were not locked in, but I did have 4wd forward, with not disengagement problems. Just the disengagement on deceleration.
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Could be any of the three components. Can still be in the t-case, but more likely the differential if it's one of the gearboxes.
But the driveshaft can definitely create harmonics that will go either way. Usually the the box with the most play in the gears.

Advance Adapters, Wild Horses, and several other Bronco vendors had many customers returning their NV3550 5-speed transmissions due to noisy internals. Nobody could really describe it other than a bad noise.
The transmissions were brand new from the factory and even the replacements sent to the customers made the same noises. Turned out to be the rear driveshaft/pinion angle in every case. Each one had at least a slight lift kit and none of them had the proper pinion angle correction shims installed.
Correcting the angle of the pinion quieted every one of the noisy transmissions.

I finally got to drive one and it sounded just like an old worn out truck transmission of the old days. Like an old SM465 that hadn't had it's oil changed in 40 years or 300,000 miles. Rattle city!
But the fact that it only happened when shifting or decelerating was the final clue that nobody had mentioned. Definite rear shaft / axle-wrap issue. Pinion was borderline too low, so when deceleration caused the pinion angle to fall a few degrees more, they got a vibration that they could not feel, or hear in their previous transmissions (tighter gear mesh) but could hear with the new looser boxes.

In the case of a front shaft misalignment, with Cougar's single joint setup a constant vibration is possible if misaligned, whereas a double-cardan setup is much more forgiving. It's also possible that due to angle changes during acceleration vs deceleration the shaft is making the vibration. Which could explain why it comes and goes based on throttle input. Then again, under load (acceleration) the gears in the transfer case are tight and less likely to rattle anyway. Lose the load, and all sorts of changes take place.
Because the noise goes away if the hubs are unlocked or the t-case is shifted out of 4wd could still be the shaft but because, even though still spinning, it's no longer under any kind of a load so is not subject to the same dynamics.

Definitely could be the differential like you said Shawner. But don't overlook the shaft in any of the scenarios until you find the source.
In the case of Cougars though, being a '79 with high-pinion front diff, being way out of alignment is less likely than an earlier low pinion front would be. Is yours a '74 as in your username Shawner? Is it a 150 or 250? Double-cardan shaft, or single? Manual or Automatic trans?

For yours Cougar, even though you have a high-pinion diff, still check the angles of the u-joints relative to each other. Or more accurately I suppose, the angle of the pinion shafts.
The transfer case output and the differential yokes should be opposite each other, but within 2 to 4 degrees I think. No more than 10 degrees apart if I'm not mistaken. Plenty of charts around showing how the relationship must be to avoid vibration.

Paul